Complementary DNA and derived amino acid sequence of the .alpha. subunit of human complement protein C8: evidence for the existence of a separate .alpha. subunit messenger RNA

Biochemistry ◽  
1987 ◽  
Vol 26 (12) ◽  
pp. 3556-3564 ◽  
Author(s):  
A. Gururaj Rao ◽  
O. M. Zack Howard ◽  
Simon C. Ng ◽  
Alexander S. Whitehead ◽  
Harvey R. Colten ◽  
...  

The nucleotide sequences coding for murine complement component C3 have been determined from a cloned genomic DNA fragment and several overlapping cloned complementary DNA fragments. The amino acid sequence of the protein was deduced. The mature β and α subunits contain 642 and 993 amino acids respectively. Including a 24 amino acid signal peptide and four arginines in the β—α transition region, which are probably not contained in the mature protein, the unglycosylated single chain precursor protein preproC3 would have a molecular mass of 186484 Da and consist of 1663 amino acid residues. The C3 messenger RNA would be composed of a 56 + 2 nucleotide long 5' non-translated region, 4992 nucleotides of coding sequence, and a 3' non-translated region of 39 nucleotides, excluding the poly A tail. The β chain contains only three cysteine residues, the α chain 24, ten of which are clustered in the carboxy terminal stretch of 175 amino acids. Two potential carbohydrate attachment sites are predicted for the α chain, none for the β chain. From a comparison with human C3 cDNA sequence (of which over 80% has been determined) an extensive overall sequence homology was observed. Human and murine preproC3 would be of very similar length and share several noteworthy properties: the same order of the subunits in the precursor, the same basic residue multiplet in the β-a transition region, and a glutamine residue in the thioester region. The equivalent position of the known factor I cleavage sites in human C3a could be located in the murine C3 α chain and the size and sequence of the resulting peptide were deduced. A comparison of the amino acid sequences of murine G3 and human alpha2-macroglobulin is given. Several areas of strong sequence homology are observed, and we conclude that the two genes must have evolved from a common ancestor.


1990 ◽  
Vol 265 (8) ◽  
pp. 4204-4209
Author(s):  
K Schott ◽  
J Kellermann ◽  
F Lottspeich ◽  
A Bacher

1987 ◽  
Vol 105 (3) ◽  
pp. 1183-1190 ◽  
Author(s):  
W S Argraves ◽  
S Suzuki ◽  
H Arai ◽  
K Thompson ◽  
M D Pierschbacher ◽  
...  

The amino acid sequence deduced from cDNA of the human placental fibronectin receptor is reported. The receptor is composed of two subunits: an alpha subunit of 1,008 amino acids which is processed into two polypeptides disulfide bonded to one another, and a beta subunit of 778 amino acids. Each subunit has near its COOH terminus a hydrophobic segment. This and other sequence features suggest a structure for the receptor in which the hydrophobic segments serve as transmembrane domains anchoring each subunit to the membrane and dividing each into a large ectodomain and a short cytoplasmic domain. The alpha subunit ectodomain has five sequence elements homologous to consensus Ca2+-binding sites of several calcium-binding proteins, and the beta subunit contains a fourfold repeat strikingly rich in cysteine. The alpha subunit sequence is 46% homologous to the alpha subunit of the vitronectin receptor. The beta subunit is 44% homologous to the human platelet adhesion receptor subunit IIIa and 47% homologous to a leukocyte adhesion receptor beta subunit. The high degree of homology (85%) of the beta subunit with one of the polypeptides of a chicken adhesion receptor complex referred to as integrin complex strongly suggests that the latter polypeptide is the chicken homologue of the fibronectin receptor beta subunit. These receptor subunit homologies define a superfamily of adhesion receptors. The availability of the entire protein sequence for the fibronectin receptor will facilitate studies on the functions of these receptors.


1981 ◽  
Vol 1 (10) ◽  
pp. 779-784 ◽  
Author(s):  
Gerard J. Arlaud ◽  
Jean Gagnon

The N-terminal amino acid sequence of human Cl̄s b chain has been extended to 52 residues. The histidine residue involved in the charge-relay system is located at position 38, whereas the ‘histidine-loop’ disulphide bridge is missing. So far, human complement subcomponents Cl̄s are the only known mammalian serine proteinases lacking this disulphide bridge.


1991 ◽  
Vol 274 (2) ◽  
pp. 473-480 ◽  
Author(s):  
M A Niemann ◽  
A S Bhown ◽  
E J Miller

Accumulating amino acid sequence data have made it increasingly evident that many essential complement proteins have potentially modifiable lysine residues in putative critical functional regions. Evidence is now presented that glucose is covalently attached to lysine-266 of purified human complement Factor B as a result of glycation. Purified B was treated with NaB3H4, which reduces such bound glucose to a mixture of radiolabelled hexitols. Amino acid analysis revealed the expected radiolabelled hexitol-lysine epimers. In addition, fluorography of dried gels resolving the major high-molecular-mass h.p.l.c.-fractionated CNBr-cleavage peptides of NaB3H4-reduced B indicated that this radioactivity was specifically associated with the 15 kDa fragment derived from the N-terminal region of fragment Bb. Amino acid sequence analysis suggested that the C-terminal lysine (residue 266 of B) of the N-terminal Lys-Lys doublet of this peptide is preferentially modified. If such glycation can subsequently be shown to occur in vivo, then perhaps this modification might also be found to affect the functional activity of B and offer a potential explanation for some of the immunopathological complications of diseases exposing key plasma proteins, such as this active-site-containing proteinase of the multimeric alternative-complement-pathway C3/C5 convertases, to long-term high concentrations of glucose, such as the decreased resistance to infection and impaired chemotaxis and phagocytosis characteristic of diabetes.


1984 ◽  
Vol 144 (1) ◽  
pp. 107-111
Author(s):  
M. Richardson ◽  
F. D. A. P. Campos ◽  
R. M. Moreira ◽  
I. L. Ainouz ◽  
R. Begbie ◽  
...  

1984 ◽  
Vol 144 (1) ◽  
pp. 101-111 ◽  
Author(s):  
Michael RICHARDSON ◽  
Francisco D. A. P. CAMPOS ◽  
Renato A. MOREIRA ◽  
Iracaema L. AINOUZ ◽  
Robert BEGBIE ◽  
...  

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